Alloy



areas July 14, 1936 UNITED STATES PATENT OFFICE Driver-Harrls Company, Han-[so poration of New Jersey R m-se ia!!- uo Drawing. Application m 21, less.

Serial No. sasss 4 Claims. (oi. 75-123) This invention relates to alloys and more par ticularly to alloys for electrical resistance units.

In the patent to Hunter No. 2,005,423,- granted June 18, 1935 there is disclosed the addition of 5 calcium to nickel-cromium and nickel-chromiumiron alloys in such amounts that a residue of calcium remains in the alloy. Likewise, in my prior latents Nos. 2,005,430, 2,005,431, 2,005,432 and 2,005,433, granted June 18, 1935, the addition of molybdenum, zirconium and calcium and cal-' cium, zirconium and aluminum to nickel-chromium and nickel-ehromium-iron alloys is disclosed. The alloys disclosed in said patents are particularly useful in resistance units that are subjected to high temperatures such as heating elements. Where a resistance unit is to be used at lower temperatures, such as in rheostats, a less expensive alloy containing less nickel and more iron is frequently used. I have found that the useful life of such alloys can be increased by the addition of various deoxidizers in such amounts that a residue of the deoxidizer or deoxidizers remains in the alloy. Thus zirconium alone may be,

added to such alloys in such amounts that from .01 to .50 percent of zirconium remains in the alloy.

The alloys to which the present invention relates are ones containing more nickel than chromium and in which the range of the metals,

nickeLchro'mium and iron, extends from 20 to 50 i .................01 percent to 2.0 percent filicon. -.01 percent to 2.0 percent 45 The alloys may or may not contain the elements, silicon and manganese, within the percentages stated above and the claims herein incorporated shall be interpreted to cover such alloys with or without the presence of silicon and manganese in the proportions that these elements are usually present in alloys of this character.

The preferred proportions of the alloying elementsare as follows:

.Nickel 35 percent Chromium 15 percent Zirconium .03 percent to .25 percent Iron Balance In this alloy, a proportion of zirconium near the 10 lower limit is preferred.

Nickel-chromium-iron alloys of the character set forth above containing zirconium within the limits set forth have been found by tests to give a greatly increased period of life over similar alloys 15 without the zirconium addition. For the purpose of determining the life of such alloys at high temperatures I have tested them by the method of test outlined in "Tentative Accelerated Life Test for Metallic Materials for Electrical Heating" 20 of the American Society for Testing Materials described in vol. 29 of the Proceedings of the Thirty-second Annual Meeting of the American Society for Testing Materia beginning on page 613. The method is substantially as follows: 25

A sample of the wire to be tested, free from Hnks, approximately twelve inches long and of about .025" diameter, is mounted vertically on the test board, the upper end being held in position by means of a suitable binding post. A 10 gram 30 weight is attached to the lower end of the specimen. A short piece of wire is attached to the 10 gram weight and projects downward into a cup 'of mercury where it may move freely up and down. A rheostat and an interrupter are connected in series with the specimen to thepower supply. The test is run on constant temperature at a standard temperature chosen for the alloy under consideration for the first twenty-four hours. Thereafter it is run on constant voltage to the 40 burnout. The life in hours up to a 10 percent increase in resistance is known as useful life while the life to the burnout is known as total life. Throughout the test the power is on two minutes and of! two minutes. This is accomplished by means of an interrupter.

In testing the alloys of my invention according to the above described method, a reference sample composed of 35 percent nickel, 15 percent chromium and balance iron and having no m- 2 I conium addition was used. The life of this sample is considered as 100 percent and the useful life of samples containing zirconium within the ranges stated was calculated therefrom. The useful life of such samples varied from 152 percent to 187 percent of the standard.

In the alloys referred to herein small amounts of phosphorus and'sulphur may be present as impurities. The nickel may also contain about 1 percent of cobalt.

I claim: i

1. A nickel-chromium-iron alloy containing substantially 35'percent nickel, substantially 15 per cent zirconium, balance iron.

3. A nickel-chromium-iron alloy containing substantially 35% nickel, substantially 15% chromium,- .01 to .50% zirconium, balance iron.

4. A nickel-chromium-iron alloy containinglO substantially 35% nickel, substantially 15% chromium, .03 to .25,% zirconium, balan'ce iron. 7

JAMES M. LOHR. 

